The goal of our proposal is to investigate paracrine fibrogenic signaling between parenchymal and non parenchymal liver cells during alcohol injury. Whereas the nonparenchymalcompartment (stellate cells) remains the major player in the development of liver, the role of the parenchymal cells (hepatocytes) in this process is drawing increasing attention. Improved understanding of the roles played by parenchymal and nonparenchymalliver cells during alcohol insult will translate into better, more effective and targeted therapeutics. However, the complex signaling exchange between different liver cell types is difficult to delineate with in vivo models or standard in vitro cell culture approaches. In this proposal, we will utilize a novel liver cell culture approach to investigate !he hypothesis that hepatic production of transforming growth factor (TGF)- plays an important role in initiating the fibrogneic program of stellate cells. This hypothesis will be explored using a novel cell culture system where cell adhesive and/or signaling molecules are imprinted into a culture substrate so as to position discrete groups of hepatocytes and stellate cells in defined locations and in close proximity to each other (see Figure 1 (A,B)). As shown in Figure 1 C, this novel cell culture dish will be used to selectively stimulate hepatocytes within the co-cultures with anti-fibrotic growth factors (GFs) (e.g. HGF and BMP7) during alcohol injury in order to investigate how GF signals delivered to hepatocytes impact activation of neighboring stellate cells. The novelty of the proposed platform lies in our ability to define interactions of two liver cell types cultured in the same dish so as to modulate the phenotype of one cell type and to study the response of the other cell type. This approach is particularly well-suited for improving our understanding of the complex heterotypic signaling underlying liver fibrosis. The novel cell culture system described here is envisioned as an enabling technology for liver toxicology studies and for high-throughput screening of liver-protective molecules.